The Excessively Detailed Headcanon Tumblr Meme
8.) Favorite indulgence and feelings surrounding indulging.
13.) Sexual orientation? And, regardless of their own orientation, thoughts on sexual orientation in general?
Jashinism does not dictate his orientation in the slightest--which is good, since Hidan goes for whoever he sees deserving, though he does tend to gravitate towards women.
34.) Thoughts on privacy? (Are they a private person, or are they prone to 'TMI?')
No, he's not a private person at all. Hidan wouldn't care if someone walked on him wanking it and he wouldn't care if he walked in on someone else wanking it. If anything, he'd ask to join. Jokingly of course.
47.) If they were to fall in love, who (or what) is their ideal?
I don't think that Hidan is quite capable of love. Sexual relationships, sure, but not love. But what he would look for in an ideal partner (given he's looking for one) is someone with a sense of adventure, their utter contentment with his faith, and lastly, someone who he can somewhat relate to.